Nu, nu&#39;-bis (p-carboalkoxybenzoyl) piperazines and polyesters therefrom



United States Patent N,N-BIS(p-CARBOALKOXYBENZOYL)PIPER- AZINES ANDPOLYESTERS THEREFROM Jack L. R. Williams and Thomas M. Laakso,Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey No Drawing. Application May 3, 1956 Serial N0. 582,339

6 Claims. (Cl. 260-75) This invention relates to monomericN,N-bis-(p-carboalkoxybenzoyl)piperazines which are useful in themanufacture of linear polyesters containing chain amide groups and tothe polyesters prepared therefrom.

A large number of polyesters are known to the art which are prepared bycondensing at least one bifunctional dicarboxylic acid, preferably inester form, with at least one glycol. The resulting highly polymericpolyesters have many desirable properties but are often somewhatditficult to process because of their inherent tendency to crystallizerapidly. In the manufacture of highly polymeric linear polyesters, it isusually desirable to cool down the molten polymer resulting from thepolymerization so as to "freeze the polymer in an amorphous form.Thereafter the uncrystallized polymer can be stretched eithertransversely or longitudinally or both in order to orient the polymer,whereupon the oriented polymer is subjected to a heat treatment to allowcrystallization in the oriented form. The readily crystallizablepolyesters such as the polymethylene terephthalates obtained bycondensation of terephthalic acid or an ester thereof with apolymethylene glycol such as ethylene glycol, or the polyesterscontaining internal amide linkages prepared by condensing one or moreglycols with an ester of N,N'-bis(p-carboxybenzoyl) alkylene diamines asdisclosed in Laakso and Williams Serial No. 504,107, filed April 26,1955, and similar well known polyesters prepared by condensing one ormore aliphatic glycols with an aromatic or aliphatic dicarboxylic acidor mixture thereof, thus pose a problem in commercial manufacture unlessthey can be modified by inclusion of another component which improvestheir quenchability characteristics without deleteriously affecting thedesirable properties of the polymers.

It is accordingly an object of this invention to provide certain new andimproved monomeric bifunctional dicarboxylic acid components which canbe polymerized with a glycol or glycols, with or without one or moreother dicarboxylic acid components to form linear condensation polymerswhich possess improved quenchability characteristics; It is anotherobject of the invention to provide, as new compounds, monomeric N,N'-bis(p-carboalkoxybenzoyl)piperazines which are useful as intermediatesfor the preparation of linear polyesters, and particularly as modifiersfor any of the well known polyesters. Another object of the invention isto improve the quenchability of the well known polyester compositions,and particularly those prepared by condensing a glycol with an aromaticdicarboxylic acid, by forming a copolyester of such reactants with thenew compounds embodying this invention. Other objects will be apparentfrom the description and claims which follow.

These and other objects are attained by means of this invention whereinit has been found that N,N-bis(pcarboalkoxybenzoyl)piperazines whereinthe alkoxy group contains 14 carbon atoms form linear polyesters bycondensation with one or more glycols and that poly- 2,852,492 PatentedSept. 16, 1958 ICC esters of improved quenchability characteristics canbe achieved by copolymerizing such piperazine derivatives in admixturewith at least one bifunctional dicarboxylic acid component and at leastone glycol. The monomeric compounds embodying this invention are ofparfined herein with glycols such as hexane-1,6-diol are noncrystallinematerials having a high viscosity, and such homopolyesters can be usedfor blending with the well known polyesters obtained by condensing aglycol with a dicarboxylic acid. Generally, however, the modification inquenchability characteristics is best achieved by co-condensing thepiperazine derivative with the glycol and other dicarboxylic acidcomponent, In such formation of copolyesters, the dicarboxylic acidcomponents desirably consist of 1-20 mol percent of the piperazinederivative and 8099 mol percent of other dicarboxylic acid component,preferably in ester form, such as terephthalic acid,4,4-bis(sulfonyl)dibenzoic acid, N,N-bis(p-carboxylbenzoyl)hexamethylene diamine, or similar alkylene diamine derivative whereinthe alkylene group contains 2-12 carbon atoms, or other well knownaromatic dicarboxylic acid component ordinarily used in polyestermanufacture. The dicarboxylic acid portion can also include one or morealiphatic dibasic acids such as succinic acid, azeleic acid or similaraliphatic dicarboxylic acid which is preferably present in a lessermolar amount than is the aromatic dicarboxylic acid.

The monomeric compounds embodying the invention are readily prepared byreacting piperazine hydrate with a p-carboalkoxybenzoyl chloride whereinthe alkoxy group contains 14 carbon atoms. The nature of the alkoxygroup does not affect the formation of the bifunctional monomer andhence the carbomethoxy, carboetho-xy, carbopropoxy and carbobutoxyderivatives can be used with equal facility for forming the monomericesters embodying the invention. The preparation of a typical monomer ofthe invention is illustrated by the 7 following example.

Example 1 Ninety-seven grams (0.5 mole) piperazine hydrate was equal thetotal volume of acid chloride solution) was added at once. One-half ofthe remaining acid chloride solution was then added after five minutesof stirring and after twenty minutes, one-half of the remaining alkalisolution and so on until all reagents had been added.

. Stirring was continued'for 20 minutes after additionN,N'-bis(p-carbobutoxybenzoyl)piperazine and similar I was complete. Thereaction mass was poured into the ice water and the white solidfiltered. The wet filter cake was crystallized from 10 liters of 3Aalcohol.

The yield of pure white N,N'-bis(p-carbomethoxy benzoyl) piperazine, M.P. 230-232 or 56.1% of the theoretical value 205 grams.

Calculated for C H O N C, 64.5; H, 5.3; N, 6.8. Found: C, 64.9; H, 4.9;N, 7.1.

The corresponding N,N' bis(p carboethoxybenzoyl) piperazine,N,N'-bis(p-carbopropoxybenzoyl)piperazine,

piperazine derivatives embodying the invention are readily prepared inexactly the same manner and are included within the scope of theinvention.

The formation of homopolyesters or copolyesters em- 0 After twentyminutes C., was grams,

bodying the monomers herein defined can be readily carried out inaccordance with the usual and well known methods for making polyestersinvolving condensation of a glycol or glycols and the dicarboxylic acidcomponents in-the presence of an esterification catalyst, thecondensation reaction being carried out until the polymerization hasproceeded to' the desired inherent viscosity which is usually of theorder of 0.4 or higher;

Thus the polymers embodying this invention can be prepared according tothe general procedures outlined by Carothers in U. S. 2,071,250, and thepiperazine derivatives embodying the invention can be used to formcopolyesters with any of the polyester forming materials disclosed byCarothers as well as those which have since been: made known in the art.In carrying out the process embodying the invention, at least two molarproportions of glycol are used for each molar proportion of thedicarboxylate monomer or monomers, with an excess of glycol preferablybeing employed. The initial ester interchange is readily effected byheating the mixture of glycol component and dicarboxylate component orcomponents in the presence of an ester interchange catalyst and at atemperature above the melting point of the reactants. The initial stageof the reaction is usually carried out at atmospheric pressure andtemperatures of 100-300 C. and preferably ZOO-300 C. for best results,although lower or higher temperatures can be employed. Generally, thedica-rboxylate component or components: are employed in the form of alower alkyl diester for: ease of removal of the alcohol which isliberated during thev initial stage, such alcohol being continuouslyremoved during the ester interchange for best results.Ifdesired,.however, free dicarboxylic acids can be used or ester-formingderivatives thereof such as salts, halides or amines. The termdicarboxylic acid components as employed herein is intended to includeboth the free acids, the esters thereof, and the ester-formingderivatives.

The process is facilitated by use of an ester-interchange catalyst, atlarge number of such catalysts being known to the art. Typicalester-interchange catalysts which can 'be employed include the metalhydrides such as calcium hydride, lithium hydride, sodium hydride, orthe like; metal oxides such, as antimony trioxide, litharge, ceriumoxide, germanium oxide and the like; double metal catalysts such aslithium aluminum stearate, calcium aluminum acetate and similarcatalysts containing an alkali or alkaline earth metal and an amphotericmetal, alcoholates of oneor more of such metals as sodium, potassium,lithium, calcium,-titanium, tin, magnesium, aluminum, zinc, and thelike, alkaline reacting salts such as borates and carbonates of thealkali metals, free metals such assodium, potassium, lithium, calcium,cobalt, tin, germanium, cerium, magnesium, lead, antimony and the likeas well as salts of these and similar metals and other well knownester-interchange catalysts such as zirconium compounds and the like.Particularly good results are obtained with the titanium compounds suchas titanium butoxide, sodium hydrogen titanium ethoxide butoxide and thelike, preferably together with water as a co-catalyst for low colorformation. The catalyst or catalyst mixture is preferably employed in aconcentration of at least 0.001% by weight based on the weight ofreactants with amounts of 0.001% to 0.05% by weight being preferred.Larger amounts of catalyst can also be used although such larger amountsusually are not necessary for optimum results;

The initial stage of the reaction is usually complete in 5-30 minutes;and, if desired, the temperature can be raised or the pressure reducedat the end of the first stage to effect completion of the removal of thealcohol liberated during the initial stage. Polymerization of the glycolester of the dicarboxylic compound is then effected to the desireddegree by continuing the heating under reduced pressure at least untilthe. polymer reaches the fiber-forming stage. The polymerization can beeffected by first obtaining a low viscosity polymer in powder form, andthen continuing the polymer build-up in powder form under vacuum, or bycontinuing the heating after the initial stage under reduced pressurewhereby the polymer remains molten until the desired molecular weightand inherent viscosity is achieved.

The polymers embodying the invention are polymerlzed until afiber-forming stage is achieved, i. e. until a rod dipped into the meltwill pull a filament when drawn from the melt. Usually for optimumresults, the polymerization is carried out until an inherent viscosityof at least 0.8 is attained with viscosities of 0.8-1.1 being preferred,although lower or higher viscosities may be desired in certain cases.The polymers of the invention usually have melting points above 200 C.The preferred polymer compositions are those having melting points inthe range of about 240 -280 C., since the polymers melting above about280 C. are ditficult to extrude and process in commercial practice.

As has been indicated, any one or more of the alkylene glycolscontaining 2-10 carbon atoms can be condensed with any one or more ofthe dicarboxylate monomers as defined herein. The resulting polymers canbe used alone or in blends of two or more of such polymers, or blends ofsuch polymers with. other polymeric materials such as polyesters,polyamides, copolyesters, polyesteramides and the like. In some cases,it is also desirable to modify the polymers by coreacting anotherdicarboxylic acid (preferably in ester form) with the glycol anddicarboxylate monomer, such other dicarboxylic acids being typified byaromatic dibasic acids such as terephthalic acid, isophthalic acid,4,4'-sulfonyl dibenzoic acid and the like or aliphatic dibasic acidssuch as adipic acid, sebacic acid, azelaic acid and the like. Thepolymers of the invention can be quenched following polymerization bycooling to a temperature below the minimum crystallization temperature.

When the homopolyesters of the piperazine derivatives are prepared, theglycol employed is desirably hexane-1,6- diol since the shorter chainglycols such as butane-1,4- diol does not give a polymer.

The polymerization proceeds rapidly and ordinarily the fiber-formingstage is reached within 10-30 minutes although the time necessary forpolymerization will vary depending upon the heating temperature, kindand amount of catalyst, and similar variable factors. The polymerizationis facilitated by removal from the reaction zone of the glycol liberatedduring the polymerization. The polymers and particularly thecopolyesters obtained by means of this invention can be extruded fromthe melt to form filaments or sheets as desired. In the-case of thecopolyesters, the resulting shaped articles are then oriented by beingstretched either laterally or longitudinally, or both, whereby a markedincrease in physical properties is obtained. The degree of stretchingwill vary somewhat depending upon the polymer composition and theproperties desired, but sheets, filaments, fibers etc. are usuallystretched 50600% of their original extruded dimension for best results.The shaped articles are usually cold drawn, i. e. drawn at a temperaturebetween the second order transition temperature and the minimumcrystallization temperature of the polymer, although, in some cases, thepolymers can be drawn at temperatures above the minimum crystallizationtemperature.

The polymers embodying the invention quench readily due to an unusuallyslow degree of crystallization. The copolyesters, when formed intofibers, filaments, sheets or the like, are characterized by exceptionalphysical andmechanical properties, including strength, flexibility andwear resistance in combination with the unusualquenchabilitycharacteristics. The copolyesters are of particular utilityin forming sheeting which can be used as support in photographicapplications. This is particularly true when the copolyester is formedfrom a piperazine derivative embodying this invention, hexane-1,6-diol,and an aromatic dicarboxylic acid such as terephthalic acid or an esterof N,N'-bis(p-carboxybenzoyl)alkylene diamine wherein the alkylene groupcontains 2-10 carbon atoms.

The use of the particular dicarboxylate piperazine derivatives insteadof a free diamine is of particular importance in practicing theinvention since the condensation thereby is a conventional polyesterreaction rather than involving competing polyester and polyamidereactions which usually result in mixtures of polymers as well aspolyester amides. The invention with regard to the polymers andcopolyesters is illustrated by the following examples which are includedfor purposes of illustration and which are not intended to limit thescope of the invention unless otherwise specifically indicated:

Example 2 To a mixture of 41 g. (0.1 mole) ofN,N-bis(p-carbomethoxybenzoyl)piperazine and 40 g. (0.3 mole) ofhexane-1,6-diol at 250 C. under nitrogen was added 0.5 ml. of catalystsolution which had been prepared by the addition of 0.2 g. of sodium and3 ml. of titanium butoxide to sufficient ethanol to bring the finalvolume to 100 ml. The temperature of the reaction mixture was held at240-270 C. for minutes, during which time ester interchange occurredwith formation of the glycol diester of the piperazine dicarboxylate andliberation of methanol. The methanol was removed from the reaction zoneas formed. Thereafter the reaction mixture was heated at 215 C. and 0.1ml. Hg pressure for 20 minutes. The resulting homopolyester had aninherent viscosity of 0.82 and a melting point of 255 C.

Example 3 The process described in the preceding example was employed toform a copolyester by the condensation of 42.1 g. (0.09 mole) of thediethyl ester of N,N'-bis- (p-carboxybenzoyl)hexamethylene diamine, 4.1g. (0.01 mole) of N,N'-bis(p-carbomethoxybenzoyl) piperazine and 40 g.(0.3 mole) of hexane-1,6-diol using 0.5 ml. of the catalyst solutiondescribed in the preceding example. The resulting copolyester had aninherent viscosity of 1.02 and a melting point of 257 C. Thiscopolyester crystallized much more slowly than the correspondingpolyester from hexane-1,6-diol andN,N-bis(p-carboethoxybenzoyl)hexamethylene diamine containing none ofthe piperazine derivative. Thus, the molten polymer could be readilyquenched upon extrusion in the form of either film or fiber and couldthereupon be oriented by drawing without the disadvantages whichaccompany partially crystallized material. Following the orientation,the polymer was readily crystallized by heating it above its minimumcrystallization temperature in an infrared oven. The oriented articlesobtained by means of this invention were extremely strong and flexible,possessed excellent dye afiinity and exhibited unusual thermaldimensional stability. The copolyesters were also useful in makingtubing, molded articles, sheeting for packaging, coating materials andthe like.

The piperazine derivatives embodying the invention showed equally goodresults when used in minor amounts to modify terephthalate polyestersand polyesters of his sulfonyldibenzoic acid. Best results were obtainedwhen the piperazine derivative amounted to from to A of the totaldicarboxylate components. Since the ester groups were split ofl? duringthe initial ester interchange, the nature of the carbalkoxy group in thepiperazine derivative had no eiiect on the course of the polymerization.Generally, the lower alkyl derivatives containing 1-4 carbon atoms wereemployed for convenience and economy and for ease in removing thealcohol liberated during the ester interchange reaction.

Thus by means of this invention a modifier component is provided whichpossesses unusual utility in modifying the quenchability characteristicsof the well known polyesters without deleteriously affecting the otherdesirable 55 properties of the polymer.

Although the invention has been described in detail 7 with particularreference to certain preferred embodiments thereof, variations andmodifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. N,N-bis(p-carboalkoxybenzoyl)piperazine wherein the alkoxy groupcontains 1-4 carbon atoms.

2. N,N-bis(p-carbomethoxybenzoyl)piperazine.

3. A condensation polymer having an inherent viscosity of at least 0.4and being the product obtained by condensing at 100-300 C. a mixture ofan alkylene glycol containing 2-10 carbon atoms with not more than anequimolar amount of acidic material consisting of l-20 l mole percent ofan N,N'-bis(p-carboalkoxybenzoyl) piperazine wherein the alkoxy groupcontains 1-4 carbon atoms and 99-80 mole percent of a bifunctionalacidic compound from the group consisting of aromatic dicarboxylic acidsand alkyl esters thereof wherein the alkyl group contains 1-4 carbonatoms.

4. A condensation polymer having an inherent viscosity of at least 0.4and being the product obtained by condensation at 100-300 C. of amixture of bifunctional reactants comprising hexane-1,6-diol with notmore than an equimolar amount of anN,N'bis(p-carboalkoxybenzoyl)piperazine wherein the alkoxy groupcontains 1-4 carbon atoms.

5. A condensation polymer having an inherent viscosity of at least 0.4,obtained by the coreaction at 100-300 C. of a mixture of hexane-1,6-diolwith not more than an equimolar amount of a mixture of -99 mole percentof an alkyl diester of N,N'-bis(p-carboxybenzoyDhexamethylene diamineand 1-20 mole percent of an N,N'- bis(p-carboalkoxybenzoyl)piperazinewherein the alkoxy group contains l-4 carbon atoms, the alkyl group ineach case containing 1-4 carbon atoms.

6. A condensation polymer having an inherent viscosity of at least 0.4obtained by coreacting at -300 C., a mixture of hexane-1,6-dio1 with notmore than an equimolar amount ofN,N-bis(p-carbomethoxybenzoyl)piperazine.

References Cited in the file of this patent UNITED STATES PATENTS2,717,896 Goldman Mar. 2, 1953

3. A CONDENSATION POLYMER HAVING AN INHERENT VISCOSITY OF AT LEAST 0.4AND BEING THE PRODUCT OBTAINED BY CONDENSING AT 100-300*C. A MIXTURE OFAN ALKYLENE GLYCOL CONTAINING 2-10 CARBON ATOMS WITH NOT MORE THAN ANEQUIMOLAR AMOUNT OF ACIDIC MATERIAL CONSISTING OF 1-20 MOLE PERCENT OFAN N,N''-BIS(P-CARBOALKOXYBENZOYL) PIPERAZINE WHEREIN THE ALKOXY GROUPCONTAINS 1-4 CARBON ATOMS AND 99-80 MOLE PRESENT OF A BIFUNCTIONALACIDIC COMPOUND FROM THE GROUP CONSISTING OF AROMATIC DICARBOXYLIC ACIDSAND ALKYL ESTERS THEREOF WHEREIN THE ALKYL GROUP CONTAINS 1-4 CARBONATOMS.